The present invention relates generally to connectors and more particularly to input-output style connectors, including connectors that are used to connect signal cables, especially high-speed signal cables, to an electronic device, such as a computer.
Many electronic devices, such as computers, include transmission lines to transmit signals from peripheral devices such as a video cameras, compact disc players or the like to the motherboard of the computer. These transmission lines incorporate signal cables that are capable of high-speed data transmissions. In most applications, the signal cable extends from either the peripheral device itself or a connector on the peripheral device to a connector mounted on the motherboard. These connectors are quite small in keeping with the trend toward reduced size of electronic devices. The size of such connectors may typically be about 8 mm by 6 mm, thereby leaving a connector designer only 48 mm2 of area in which to develop appropriate connector structure and components in order achieve a desired level of performance of the connector.
Signal cable construction may use what are known as one or more twisted pairs of wires that are twisted together along the length of the cable, with each such twisted pair being encircled by an associated grounding shield. These twisted pairs typically receive complimentary signal voltages, i.e., one wire of the pair may see a +1.0 volt signal, while the other wire of the pair may see a xe2x88x921.0 volt signal. As signal cables are routed within a computer, they may pass by or near electronic devices on the computer motherboard which create their own electric field. These devices have the potential to create electromagnetic interference to transmission lines such as the aforementioned signal cables. However, this twisted pair construction minimizes or diminishes any induced electrical fields and thereby eliminates electromagnetic interference.
In one current application, these signal cables are manufactured in three different speeds for use with peripheral devices and these three speeds are 800, 1600 and 3200 megabits per second. If the speed of the cable is known to the electronic device, the device may switch to various internal circuits to match the transmission speed capability of the cable. It is therefore desirable to incorporate a means to determine the speed of the cable into the connector itself.
In order to maintain electrical performance integrity from the cable to the circuitry of the device, it is further desirable to obtain a substantially constant impedance throughout the transmission line, from circuit to circuit and to avoid large discontinuities in the impedance of the transmission line. It is known that it is difficult to control the impedance of a connector inasmuch as the impedance of a conventional connector typically drops through the connector and across the interface of the two mating connector components. It is therefore desirable to maintain a desired impedance throughout the connector and its connection to the circuit board.
The present invention is therefore directed to a cable connector for providing a connection between high-speed cables and a printed circuit board that provides a reliable connection with a high level of performance.
Accordingly, it is a general object of the present invention to provide an improved connector for high-speed data transmission connections in which the impedance discontinuity through the connector is minimized so as to better attempt to match the impedance of the transmission line.
Another object of the present invention is to provide a connector for use in conjunction with signal cables that provides a connection between two twisted pairs of wires of the cable, the connector having an improved electrical performance due to its structure, thereby eliminating the need to modify circuitry on the circuit board to which the connector is mounted in order to save space on the circuit board and reduce manufacturing costs.
A further object of the present invention is to provide an improved connector for effecting a connection between a transmission line having at least one pair of differential signal wires and an associated ground and like connections on a circuit board, wherein the connector includes two signal terminals for contacting opposing signal terminals terminated to the differential signal wires and a ground terminal disposed adjacent to the signal terminals for contacting an opposing ground terminal of the associated ground in order to provide a contact ground reference throughout the connector and onto the circuit board.
It is a further object of the present invention to provide such a connector wherein, by varying the size of the ground terminal and its location relative to its two associated signal wires, the impedance of the connector may be xe2x80x9ctunedxe2x80x9d to obtain a preselected impedance through the connector.
Yet another object of the present invention is to provide a connector for connecting cables, such as those of the IEEE 1394 type, to a circuit board of an electronic device, wherein the connector has a number of discrete, differential signal wires and associated grounds equal in number to those contained in the cables, the ground terminals of the connector being configured in size and location with respect to the signal terminals of the connector in order to minimize the drop in impedance through the connector.
Another object of the present invention is to provide a connector assembly of interengaging first and second connectors wherein the first connector includes a means in determining status information, such as for example, the transmission speed of a high speed cable, and the second connector having a terminal to convey such status information to a circuit on the circuit board.
Yet still another object of the present invention is to provide an input-output connector assembly having interengaging plug and receptacle connectors that when engaged, provide a connection between a cable and a printed circuit board, wherein one of the connectors is terminated to the cable and the other connector is terminated to the circuit board, the one connector having means for conveying status information of the cable through the other connector to the circuit board, such as the speed of the cable, the one connector including a nest formed in the housing thereof, and the nest having an electronic component for interconnecting a status information terminal with an associated terminal of the one connector, the component affecting a signal transmitted through the other terminal in a manner that indicates the status information to circuitry on the circuit board.
A still further object of the present invention is to provide a connector having a socket end for receiving a corresponding plug portion of a signal cable, the socket having inner and outer shields spaced apart from each other to facilitate levels of connection, including isolation, direct galvanic connection and electronic networks.
Another object of the present invention is to provide an improved connector having a double shield structure, with inner and outer shields being separated by an intervening insulator, the connector including an electronic network interconnecting the inner and outer shields together that may be used to block DC current flow between the shields, to dissipate electrostatic charges acquired by the connector and/or to limit overvoltage conditions, etc.
In order to obtain the aforementioned objects, one principal aspect of the invention that is exemplified by one embodiment thereof includes a first connector structure which has a housing that supports, for each twisted pair of wires in the mating signal cable, three conductive terminals in a unique pattern of a triplet, with two of the terminals carrying differential signals, and the remaining terminal being a ground terminal that serves as a ground reference to the differential pair of signal wires. A second connector is provided that mates with the first connector and this second connector also has a triplet pattern of conductive terminals that are terminated to signal and ground wires of the cable.
The arrangement of these three terminals within the connector permits the impedance to be more effectively controlled throughout the first connector, from the points of engagement with the cable connector terminals to be points of attachment to the circuit board. In this manner, each such triplet includes a pair of signal terminals that are aligned together in side-by-side order, and which are also spaced apart a predetermined distance from each other. A contact portion of the ground terminal extends in a different plane than that of like portions of the signal terminals, while the remainder of the ground terminal extends between the signal terminals, but in the same plane as the signal terminals.
The width of this ground terminal contact portion and its spacing from the signal terminals may be chosen so that the three terminals may have desired electrical characteristics such as capacitance and the like, which affects the impedance of the connector. By this structure, a greater opportunity is provided to reduce the impedance discontinuity which occurs in a connector without altering the mating positions or the pitch of the differential signal terminals. Hence, this aspect of the present invention may be aptly characterized as providing a xe2x80x9ctunablexe2x80x9d terminal arrangement for each twisted pair and ground reference wire arrangement found in either a cable or in other circuits.
In another principal aspect of the present invention, two such tunable triplets may be provided within the connector housing, but separated by an extent of dielectric material, such as the connector housing, an air gap, or both. In order to maximize the high speed performance of the connector, the signal and ground terminals are preferably all similarly flat contacts that are cantilevered from their associated body portions so that the ground terminal contact portions may be selectively sized with respect to their associated signal terminals to facilitate the-tuning of the terminals to obtain the optimum desired impedance. When two such triple terminal sets are utilized in the connectors of the present invention, the power terminals of the connector may be situated between the two triple terminal sets at a level equal to that of the ground terminals so as not to interfere with the signal terminals.
In another principal aspect of the present invention, one of the interengaging connectors may be provided with multiple shields arranged in an inner and outer relationship and separated by an intervening insulative member. These two shields, on one embodiment, include a series of tabs to which electronic components may be applied to form a desired return. In another embodiment of this two-shield concept, the two shields may be interconnected by a circuit board, conventional, flexible or other onto which preselected electronic components may be added. In still another embodiment, the inner shield may be formed as part of the outer shield so that a direct connection is obtained between the two shields. In yet another embodiment, the inner shield may have mounting feet interior of the mounting feet of the outer shield.
In still another principal aspect of the present invention, and as exemplified by another embodiment thereof, a status information detection feature is provided within the confines of a plug connector that identifies certain information on the status of a cable, circuit, or other component connected to the plug connector, to the circuit board of the electronic device. The status information may pertain to the speed of the cable terminated to the plug connectors and may serve to identify one of three typical cable speeds: 800, 1600 or 3200 megabits per second.
In this type of construction, one or more terminals of the plug connector are dedicated to the status information aspect. The housing of the plug connector may be provided with a nest, or recess, that extends between a terminal dedicated to status information and another terminal, such as the power ground terminal. The nest holds an electronic component such as a resistor, a capacitor or the like in an orientation so that the electronic component bridges, or shorts, the two aforementioned terminals. The status terminal of the plug connector is engaged by an opposing status terminal located in an opposing mating connector. This status terminal is terminated to the circuit board so that the status information terminal of the plug connector, in effect, completes a selected status circuit of the circuit board.
When a resistor is used as the bridging component, the circuit board circuitry may read voltage passed through the status terminal and read its value to determine the speed of the cable. When the electronic bridging component is a capacitor, the circuit board circuitry is able to read the voltage rise over time transmitted through the status terminal and thereby determine the cable speed.
In still another principal aspect of the present invention, a noise reduction feature is incorporated by capacitively coupling the power out and return terminals of the connector together in order to maintain them at the same potential during operation of high speed data transmission. A capacitor is used to couple these two terminals together which facilitates AC current flow, while blocking DC or steady state current flow.
These and other objects, features and advantages of the present invention will be clearly understood through consideration of the following detailed description.